Modified phenol-formaldehyde resole resins, methods of manufacture, methods of use, and articles formed therefrom

ABSTRACT

A method for the manufacture of a modified phenolic-aldehyde resin composition, comprises reacting a base with a phenolic compound to produce a phenolate medium; adding an aldehyde source to the phenolate medium wherein the initial mole ratio of aldehyde to phenolic compound is about 0.7:1 to about 1.4:1; heating the aldehyde source and phenolate medium for a time and at a temperature sufficient to yield an aldehyde-phenolate medium with a level of free aldehyde of less than about 0.5% of the total mass on a liquids basis; adding a urea-aldehyde condensate to the aldehyde-phenolate medium; and condensing the resulting urea-aldehyde-phenolate medium, wherein the modified phenolic-aldehyde resin composition is not infinitely dilutable in water. A modified phenolic-aldehyde resin prepared by this method is also disclosed, as are articles prepared therewith.

RELATED APPLICATION DATA

This application claims the benefit of U.S. Provisional Application Ser.No. 60/624,229 filed Nov. 2, 2004, the entire contents of which arehereby incorporated by reference.

BACKGROUND

This disclosure relates to phenol-formaldehyde resole resins, theirpreparation, use, and articles formed therefrom.

Phenol-formaldehyde resole resins are of utility in a wide range ofapplications due to their excellent physical properties, including theirdurability, water resistance, bond strength, and the like, as well astheir low cost and ease of manufacture and use. Phenol-formaldehyderesole resins have accordingly been used in the manufacture of laminatesand consolidated wood products such as plywood and engineered lumber,particle board, fiber board, and oriented strand board, as well as inproducts such as fiberglass insulation, abrasive coatings, frictionbinders, foams, foundry binders, and petroleum recovery binders. Theyare also used as paper saturating resins for oil filters, overlay, paintroller tubes, and the like.

While a wide variety of phenol-formaldehyde resole resins have beendeveloped and are suitable for their intended purposes, environmentaland industry standards demand ever-increasing improvement in bothenvironmental compliance and physical properties of the resins.Reduction in formaldehyde emissions has proved particularly difficultwithout significantly adversely affects the advantageous properties ofthe resins, cost, and/or manufacturing time. For example, formaldehydescavengers such as urea, ammonia, melamine, various primary andsecondary amines, dicyandiamide, and other amino-based modificationshave been added to resoles. These are typically post-added to the resinat the resin manufacturers' or at the customers' plant, resulting in lowefficiencies. Post-addition of urea can cause trimethylamine odors,which arises from incomplete reaction of urea. Post-addition of ammoniaas a scavenger can lead to lower water dilutability, unwanted precure,and ammonia odor.

Other approaches include post-addition of a cyclic urea prepolymer, asdescribed in U.S. Pat. No. 6,114,491. This prepolymer is formed from andcontains ammonia. A process of reacting a first amino-based scavengerunder acidic conditions and a second amino-based scavenger at neutral orslightly basic conditions is described in U.S. Pat. No. 4,757,108. Aprocess requiring adding ammonia, specifically at the site of the resinmanufacturer, before the addition of urea, is described in U.S. Pat. No.5,300,562.

There accordingly remains a need in the art for compositions and methodsthat will lower aldehyde (specifically formaldehyde) emissions fromphenol-formaldehyde resole resins while maintaining or improvingstability, cure efficiency, and/or advantageous physical properties suchas durability, water resistance, and or bond strength.

The most common commercial scavengers are chemical species containing aprimary or secondary amine functionality, for example urea, ammonia,melamine, and dicyandiamide

There also remains a particular need in the art for improvedphenol-formaldehyde resole resins for use as plywood and engineeredlumber adhesives. Urea has been added to plywood and engineered lumberresins and adhesives to improve pre-press tack, bond quality, cost,assembly time tolerance, and reduce formaldehyde emissions, generally inamounts of up to about 5 wt %, based on the solid weight of urea to thetotal resin weight (at 41% solids, including the urea). However, whenurea is used at higher levels, the phenol-formaldehyde resole resin mayrequire a long assembly time (time between application of the adhesiveand when the panels are hot pressed or pre-pressed), to eliminate dryoutof the adhesive.

A need also exists with respect to particle board, for example orientedstrand board (OSB). Spray dried oriented strand boards (OSB) and waferboard resins are very sensitive to any extender or filler that is usedin the resin. Many attempts have been made to use small amounts of ureaor urea-formaldehyde resins as extenders in various phenol-formaldehydeand phenol-melamine-formaldehyde resins, but is has been found that theurea may interfere with the ability of the resin to be spray dried,and/or adversely affect durability. Urea in these applications is thustypically limited to 1 wt %, for the purpose of scavenging freeformaldehyde.

Phenol-formaldehyde resole resins are also used to manufacture highpressure laminates. Laminates that are post-formed (thermoformed) intomore complex shapes after the pressing process is complete may require aless brittle resin. Brittle laminates also tend to chip and break whenthey are cut to size or machined prior to use or can be more breakageprone during installation and use. This is also unacceptable to theconsumer. Another drawback in the laminating industry is the release ofvolatile organic components into the atmosphere during the B-stagingprocess, including formaldehyde and phenol. Typical levels of freephenol in the phenol-formaldehyde resole resin used to impregnate thekraft core paper are about 5 to about 15 wt %. One method to reduce thefree phenol level in the base phenol-formaldehyde resole resin is toincrease the amount of formaldehyde (relative to the phenol) in theresin as manufactured. Unfortunately this can result in a more brittleresin that when cured is unacceptable for manufacturing postforminglaminates. There accordingly remains a need for resins that can be usedin the manufacture of paper laminates that have low phenol andformaldehyde emissions and that are not brittle upon cure.

SUMMARY OF THE INVENTION

The above-described drawbacks and disadvantages of the prior art arealleviated by a phenol-formaldehyde resole resin modified with aurea-aldehyde condensate, referred to herein as a modifiedphenolic-aldehyde resin.

In an embodiment, a method for the manufacture of a modifiedphenolic-aldehyde resin composition, comprises reacting a base with aphenolic compound to produce a phenolate medium; adding an aldehydesource to the phenolate medium wherein the initial mole ratio ofaldehyde to phenolic compound is about 0.7:1 to about 1.4:1; heating thealdehyde source and phenolate medium for a time and at a temperaturesufficient to yield an aldehyde-phenolate medium with a level of freealdehyde of less than about 0.5% of the total mass on a liquids basis;adding a urea-aldehyde condensate to the aldehyde-phenolate medium; andcondensing the resulting urea-aldehyde-phenolate medium, wherein themodified phenolic-aldehyde resin composition is not infinitely dilutablein water.

In another embodiment, a modified phenolic-aldehyde resin comprises thereaction product of the combination of: a phenolic compound; about 0.01to about 0.1 moles of base catalyst per mole of phenolic compound; analdehyde, wherein the initial molar ratio of aldehyde:phenolic compoundis about 0.7:1 to about 1.4:1; and a urea-aldehyde condensate, thecombination being reacted at a temperature of about 70 to about 90° C.for a time effective to form a modified phenolic-aldehyde resin that isnot infinitely dilutable in water, and wherein the final molar ratio ofaldehyde:phenolic compound in the modified phenolic-aldehyde resin isabout 0.7:1 to about 4.5:1.

In another embodiment, a composition comprises an additive and amodified phenolic-aldehyde resin composition comprising the reactionproduct of the combination of: a phenolic compound; about 0.01 to about1.0 moles of base catalyst per mole of phenolic compound; an aldehyde,wherein the molar ratio of aldehyde:phenolic compound is about 0.7:1 toabout 1.4:1; and a urea-aldehyde condensate, the combination beingreacted at a temperature of about 70 to about 90° C. for a timeeffective to form a modified phenolic-aldehyde resin that is notinfinitely dilutable in water.

DETAILED DESCRIPTION OF THE INVENTION

This invention describes the manufacture of a modified phenolic-aldehyderesin that has low free formaldehyde content. By introduction of aurea-formaldehyde condensate to a phenol-formaldehyde resole resin, aproduct can be made that has low free formaldehyde content atmanufacture and during storage, and that emits low formaldehyde levelsduring processing and curing. In particular, stable modifiedphenolic-aldehyde resins having excellent physical properties andreduced emissions may be prepared by addition of a urea-aldehydecondensate during formation and/or use of the phenol-formaldehyde resoleresin. The resins are not infinitely dilutable in water, but have goodsolution stability under storage conditions at high solids.

As used herein, the term “condensate” refers to the condensation productof urea and an aldehyde, and may be used interchangeably with the term“urea-aldehyde condensate”; the terms “urea-formaldehyde concentrate”and “UF concentrate” are used to describe the specific condensate ofurea and formaldehyde, and may be used interchangeably; the term“phenol-formaldehyde resole resin” refers to the base catalyzed reactionproduct of a hydroxy aromatic compound and an aldehyde, and which maycontain co-reactants such as urea or dicyandiamide, but which does notcomprise urea-aldehyde concentrate; the term “modified phenolic-aldehyderesin” refers to the reaction product of the resole resin (with orwithout co-reactants) and a urea-aldehyde condensate; the term “modifiedphenolic-aldehyde resin composition” refers to a liquid reaction productcomprising the modified phenolic-aldehyde resin; the terms “premix” and“premix composition”, where used, refer to the combination (in solution)of a resole resin or modified phenolic-aldehyde resin with added urea,and may be used interchangeably; and the term “manufacturingcomposition”, refers to the combination of a modified phenolic-aldehyderesin with other additives such as, for example, plasticizer, filler,and thermal acid generators.

The urea-aldehyde condensate is formed by the reaction of urea and areactive aldehyde source under alkaline conditions. The urea may bederived from a variety of commercially available forms, for examplesolid urea, such as prill, and aqueous urea solutions. Reactivealdehydes such as formaldehyde, mixtures comprising formaldehyde, orother sources of formaldehyde, are specifically useful. Formaldehyde maybe used in the form of a gas, a formalin solution (an aqueous solutionof formaldehyde) in typical concentrations of about 37 to about 60 wt %(weight %), as paraformaldehyde (solid, polymerized formaldehyde), or asa mixture comprising any of the foregoing. Reactive aldehydes can alsobe substituted in whole or in part for formaldehyde to produce theaqueous urea-aldehyde condensate. Examples of other reactive aldehydesthat may be used include acetaldehyde, propionaldehyde, furfuraldehyde,glutaraldehyde, and benzaldehyde. Mixtures comprising at least one ofthe foregoing may also be used. The aldehyde is typically used in anamount of about 4 to about 6 moles per mole of urea, with an optimumdependent on the particular application. In one embodiment, an exampleof the urea-formaldehyde condensate has a formaldehyde-to-urea ratio ofabout 3:1 to about 6:1, preferably about 4:1 to about 6:1 and morepreferably about 5:1.

The relative amounts of aldehyde, urea, and water used to form theurea-aldehyde condensate and effective times and temperature forreaction will depend on the desired concentrations of formaldehyde,urea-aldehyde condensate, and water in the urea-aldehyde condensate.These relative ratios will in turn depend on the type ofphenol-formaldehyde resole resins used and the desired end properties ofthe resin. In general, the urea-aldehyde condensate may comprise about0.1 to about 50 wt %, specifically about 10 to about 30 wt %, morespecifically about 20 to about 25 wt % free formaldehyde; about 20 toabout 90 wt %, specifically about 50 to about 75 wt %, moresspecifically about 60 to about 65 wt % urea-formaldehyde; and about 5 toabout 60 wt %, specifically about 8 to about 35 wt %, more specificallyabout 12 to about 18 wt % water.

In one embodiment, the urea-aldehyde condensate comprises urea,formaldehyde, and water, and is a urea-formaldehyde condensate. Aparticular example is where the urea-formaldehyde condensate comprisesabout 60 wt % formaldehyde, about 25 wt % urea, and about 15 wt % water.In another example, the condensate comprises about 50 wt % formaldehyde,about 21 wt % urea, and about 29 wt % water. In another example, theurea-formaldehyde condensate comprises about 65 wt % formaldehyde, about25 wt % urea, and about 10 wt % water. It will be appreciated by thoseskilled in the art that the formaldehyde content of the composition isdistributed at least between formaldehyde reacted with the urea to formmethylol groups, and free formaldehyde. The distribution ratio of theseforms of the formaldehyde will be influenced by the ratios offormaldehyde, urea, and water, and additionally by reaction time,temperature, processing conditions such as the use of a vacuum strip orreflux, and concentration. A typical amount of free formaldehyde for asingle embodiment may be about 15 wt % to about 30 wt % of theurea-aldehyde condensate, specifically about 20 wt % to about 25 wt %.It will also be appreciated by one skilled in the art that additionalvariations of the ratio of formaldehyde, urea, and water, as well asvariations in reaction conditions as described above, may be used, whichwill provide a urea-aldehyde condensate that acts within the scope ofthe present disclosure.

In general, these urea-aldehyde condensates may be obtained by mixingabout 20 to about 80 wt %, specifically about 30 to about 70 weightpercent, more specifically about 50 to about 65 wt % formaldehyde, about5 to about 70 wt %, specifically about 15 to about 50 weight percent,mores specifically about 20 to about 40 wt % urea, and about 0.01 toabout 1.0 wt %, specifically about 0.02 to about 0.5 weight percent,more specifically about 0.03 to about 0.4 wt % catalytic base at atemperature of about 40 to about 100° C., specifically about 75 to about85° C. if processing in batch mode, for about 3 to about 10 hoursdepending on process.

The urea-aldehyde condensates may be prepared in a container such as alaboratory flask or plant reactor. Additionally, urea-formaldehydecondensate may be prepared using a continuous flow process. Such aprocess may comprise adding gaseous formaldehyde, 50 wt % urea inaqueous medium, and a base catalyst to an absorber column. Water may beremoved from the condensate during this process. Such urea-formaldehydecondensates may also be obtained commercially. An example of a suitablecomposition is Casco® UF85 concentrate from Hexion Specialty Chemicals,Inc., formerly known as Borden Chemical.

An example of the preparation of a urea-formaldehyde condensate is asfollows: A flask is charged with 124.5 g of a 50 wt % solution offormaldehyde, and the temperature of the solution is raised to about 60to about 70° C. The formaldehyde solution is adjusted to a pH of about8.5 to about 9.2 by addition of about 0.7 g of 50 wt % sodium hydroxidein water. About 25 g of urea is then added, and the temperature isslowly raised to about 78 to about 82° C., and the temperature of thereaction is maintained at about 80° C. for a hold time of about 30minutes. During this hold, the pH is checked about every 10 minutes, andis adjusted to maintain a reaction pH of about 7.2 or greater byaddition of an effective amount of 25 wt % sodium hydroxide. After thehold time, the reaction is cooled to about 45° C. Water is distilled offthe reaction to a refractive index endpoint for the resulting condensateof about 1.469 to about 1.472, where it is desirable to approach thehigher number in the event that it is necessary to add formaldehyde.Using the above proportions, the amount of distillate removed, whichgives this refractive index endpoint, is about 52.4 g. The amount offree formaldehyde is determined by using the sodium sulfite method andis adjusted to about 20 to about 25 wt %, more specifically about 21 toabout 23 wt % by further addition of formaldehyde.

The urea-aldehyde condensate is used with a phenol-formaldehyde resoleresin to form the modified phenolic-aldehyde resin. Phenol-formaldehyderesole resins may be prepared by the reaction of a hydroxy-functionalaromatic compound (hereinafter “phenolic compound”), for example phenol,with an aldehyde or aldehyde condensate, for example formaldehyde, underalkaline reaction conditions. Examples of aldehydes for this purpose arein part described above, where these aldehydes may be suitable for usein the formation of either or both of the urea-aldehyde condensate andthe phenolic-aldehyde resole resin. For convenience, all suchphenolic-aldehyde resins may be referred to herein as“phenol-formaldehyde resole resins.” It is to be understood that whilethe terms “phenol” and “formaldehyde” may be used in the followingdescription for convenience, the discussion also applies to otherhydroxy-functional aromatic compounds, reactive aldehydes, and mixturesas described herein. Thus, other hydroxy-functional aromatic compoundsincluding monophenolic and dihydric phenolic compounds can be used, orused in addition to phenol itself. Examples of substituted monophenolsthat can be used include alkyl-substituted monophenols such as o-cresol,m-cresol, p-cresol, 3,5-xylenol, 3,4-xylenol, 3,4,5-trimethyl phenol,3-ethyl phenol, 3,5-diethyl phenol, p-butyl phenol, 3,5-dibutyl phenol,p-amyl phenol, p-octyl phenol, and the like; cycloalkyl-substitutedmonophenols such as p-cyclohexyl phenol, 3,5-dicyclohexyl phenol, andthe like; alkenyl-substituted monophenols; aryl-substituted monophenolssuch as p-phenyl phenol; alkoxy-substituted monophenols such as3,5-dimethyoxyphenol, p-ethoxy phenol, p-butoxy phenol,3,4,5-trimethoxyphenol, and the like; aryloxy-substituted monophenolssuch as p-phenoxy phenol; halogen-substituted monophenols such asp-chlorophenol; and polycyclic monophenols such as naphthol, anthranol,and substituted derivatives thereof. Similarly, dihydric phenols such ascatechol, resorcinol, hydroquinone, bisphenol A and bisphenol F can beused. Mixtures comprising at least one of the foregoinghydroxy-functional aromatic compounds may be used. Phenol itself isspecifically useful, as well as mixtures which include phenol.

Similarly, other reactive aldehydes as described above can besubstituted in whole or in part for formaldehyde to produce theformaldehyde resole resin. Formaldehyde or mixtures comprisingformaldehyde are specifically useful. The formaldehyde may be used inthe form of a gas, a formalin solution (an aqueous solution offormaldehyde, with typical concentrations of about 37 to about 60 wt %of formaldehyde), and/or paraform (paraformaldehyde, or solid,polymerized formaldehyde).

Additionally, nitrogenous compounds with crosslinkable functional sitesmay be used either in combination with the hydroxy-functionalizedaromatic compounds described above. Examples of such nitrogenouscompounds with a suitable reactivity include amines such asethylenediamine, propylenediamine, 1,3-pentanediamine,1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine,bis-(2-aminoethyloxy)ethylene, melamine, urea, dicyandiamide, and cyclicureas such as ethyleneurea, propyleneurea, trimethyleneurea, andglycoluril. Urea, dicyandiamide, or melamine are useful, as well asmixtures which include urea, dicyandiamide, and melamine.

Alkaline reaction conditions may be established by adding an alkalinecatalyst to an aqueous solution of the phenol and/or phenol andformaldehyde reactants. Suitable alkaline catalysts include those knownin the art for the manufacture of resole resins, and include, forexample, alkali and/or alkaline earth metal hydroxides such as lithiumhydroxide, sodium hydroxide and potassium hydroxide; alkaline earthmetal oxides such as lime; alkali metal carbonates such as sodiumcarbonate and potassium carbonate; and certain amines. Based onconsiderations of cost and availability, sodium hydroxide and/orpotassium hydroxide is used most often.

Effective amounts of alkaline catalyst are known to those skilled in theart. Typically, at least about 0.005 mol of alkaline catalyst per mol ofphenol is used, specifically an amount between about 0.01 and about 1mol of alkaline catalyst per mol of phenol, depending on theapplication. All of the catalyst can be added initially to the phenoland the formaldehyde provided it is added slowly to control theexothermic reaction, or the catalyst can be added incrementally in twoor more additions or continuously over a defined time period. It isnormally recommended that the catalyst be added in three to five or moreadditions to maintain control of the reaction. Use of a relatively highlevel of catalyst may reduce residual monomers and simultaneouslyminimize the proportion of high molecular weight species in the product.For example, the amount of catalyst may be about 0.01 mol to about 0.60mol, specifically about 0.02 mol to about 0.20 mol of catalyst per molof phenolic compound.

In one embodiment, as a typical process for the manufacture ofphenol-formaldehyde resole resins, an initial aqueous reaction mixturemay be prepared by first combining a hydroxy-functional aromaticcompound and a basic polymerization catalyst in an aqueous solution toprovide a phenolate medium. The reactive aldehyde is then added to thephenolate medium (also referred to herein as the “initial aqueousreaction mixture”). Alternatively, the initial aqueous reaction mixturemay be prepared by mixing a hydroxy-functional aromatic compound and areactive aldehyde, followed by addition of a basic polymerizationcatalyst. In an advantageous aspect to the process, the initial ratio ofaldehyde to phenolic compound is kept low, to push the equilibrium ofthe reaction to a greater degree of conversion of the initial aldehydecharge. A useful initial molar ratio of aldehyde to phenolic compoundfor this purpose is about 0.7:1 to about 1.4:1, more specifically about0.9:1 to about 1.2:1. One skilled in the art will appreciate that amolar excess of phenol will encourage lower free formaldehyde content,thereby obviating the need for addition of an aldehyde scavenger. Oneskilled in the art will further appreciate that a desired stoichiometryis in part also defined as the presence of equivalent molarconcentrations in the reaction medium at a given instant in time, andmay be affected by other factors such as heat, reaction time, andremoval of by-products from the reaction which would affect theequilibrium of the reaction. In light of these constraints, it is withinthe skill of a practitioner in the art to determine the appropriateratio of aldehyde to phenolic compound for a particular application, andto select the appropriate reaction conditions.

Use of a more limited formaldehyde charge in the initial stage of thepolymerization defers the introduction of additional aldehyde, which maybe useful in building the desired properties of the resin, to a laterstage. A source of additional aldehyde may be an additional charge ofthe aldehyde itself, of a self-condensate such as paraformaldehyde, orof a condensate with an additional component such as a condensate ofurea and formaldehyde.

After completion of the addition of the aldehyde, the temperature of thephenolate medium is maintained within a range effective to completemethylolation and effect condensation, until a predetermined endpoint isachieved. The temperature is desirably maintained sufficiently high sothat the condensation reaction can occur rapidly, without significantbuildup of molecular weight. The temperature of the first aqueousreaction mixture may, for example, be maintained at about 50 to about100° C.; more specifically at about 65 to about 95° C.; still morespecifically at about 75 to about 85° C.

The endpoint can be determined by an analytical technique that samplesthe extent of condensation, for example gel permeation chromatography(GPC) or water tolerance. The endpoint is predetermined based on thedesired properties of the resulting phenol-formaldehyde resole resin,and is generally chosen so as to simultaneously minimize the residualfree monomer content of the resin while maximizing the ability toachieve the desired molecular weight in consideration of such propertiesas paper penetration, cure time, application techniques other suchparameters. The endpoint can be determined by an analytical techniquethat samples the extent of condensation, for example gel permeationchromatography (GPC).

The urea-aldehyde condensate may be combined with thephenol-formaldehyde resole resin at any point during, after, or bothduring and after the process of manufacture and used as described inmore detail below. The point in the process for addition of theurea-aldehyde condensate is dependent upon the amount of formaldehydepresent in the phenol-formaldehyde resole resin, on the amount of theurea-aldehyde condensate to be added, and is considered in view of thedesired molecular weight of the final resin and the amount of freemonomer desired. It is within the skill of one versed in the art todetermine the appropriate point of introduction of the condensate.

In one embodiment, the urea-aldehyde condensate is added when thepredetermined endpoint is reached. Adding the urea-aldehyde condensatehas several advantages over adding solid urea and formaldehyde solution.For example, the urea-aldehyde condensate is a more concentrated sourceof formaldehyde. Commercially available formaldehyde solutions typicallycontain about 50% formaldehyde by weight versus the about 60% by weightcontained in the material. The additional formaldehyde gives the finalmodified phenolic-aldehyde resin product the reactivity and polymercrosslink density desired to produce laminate with acceptable properties(i.e., water resistance, formability, and impact resistance). Inaddition, because the urea is added in a pre-reacted form withformaldehyde prior to addition to the phenol-formaldehyde resole resin,and where there is essentially no unreacted urea, a high urea content isobtained in the final resin product without compromising resinperformance in the end application. Since urea is a low cost component,there is commercial advantage in urea-modified phenol-formaldehyderesole resins (i.e., modified phenolic-aldehyde resins) that performsimilarly to unmodified phenol-formaldehyde resole resins. Since lesswater is added to the reaction mixture, less is required to be removedby distillation. Additionally, the polymerization reactions proceed morereadily.

In another embodiment, the urea-aldehyde condensate is added when theresidual free aldehyde content of the reaction is less than about 0.5 wt%, specifically less than about 0.2 wt %, more specifically less thanabout 0.1 wt %, still more specifically less than about 0.05 wt %, andstill more specifically less than about 0.01 wt %. In addition, theresidual free aldehyde content is greater than about 0.01 ppm,specifically greater than about 0.1 ppm, more specifically greater thanabout 1 ppm, still more specifically greater than about 5 ppm, and stillmore specifically greater than about 10 ppm. This procedure results inresins having very a low free formaldehyde value, therefore reducing theformaldehyde emissions, without the use of aldehyde scavengers.

The amount of urea-aldehyde condensate added to the phenol-formaldehyderesole resin will depend on the types and ratios of starting materials,as well as the desired properties of the final modifiedphenolic-aldehyde resin. Typical amounts may be about 0.1 to about 30 wt%, specifically about 1 to about 20 wt %, more specifically about 5 toabout 15 wt %, as based on the wet resin. During and after addition ofthe urea-aldehyde condensate, the reaction is continued at a temperatureand for a time effective to blend and/or further condense the resin andthe condensate. Effective temperature and times will depend upon thetypes and ratios of starting materials, as well as the desired resinproperties. In general, this portion of the process may be conductedabout 50 to about 100° C., specifically about 75 to about 85° C., forabout 5 minutes to about 4 hours, specifically about 30 minutes to about3 hours, more specifically about 60 to about 150 minutes.

The final aldehyde ratio in the modified phenolic-aldehyde resin aftercombination of the phenol-formaldehyde resole resin and theurea-aldehyde condensate is about 0.7 to about 4.5 moles of the aldehydeper mole of phenolic compound (i.e., 0.7:1 to 4.5:1), more specificallyabout 0.7 to about 2.5 moles of the aldehyde per mole of phenoliccompound (i.e., 0.7:1 to 2.5:1) in the modified phenolic-aldehyde resin,but with the optimal ranges being dependent on the particularapplication. As used herein, “overall formaldehyde to phenol ratio”describes the ratio of formaldehyde to phenol present after modificationof the phenol-formaldehyde resole resin with the urea-aldehydeconcentrate, and is also referred to herein as the “final formaldehydeto phenol ratio”. In an example of one embodiment, a phenol-formaldehyderesole resin wherein the ratio of formaldehyde to phenol is about 1.1:1is combined with a urea-formaldehyde condensate wherein the ratio offormaldehyde to urea is about 4.8:1, in proportions sufficient toproduce an overall (i.e., final) formaldehyde to phenol ratio of about1.425:1 in the resulting modified phenolic-aldehyde resin. In thisinstance, the amount of formaldehyde added as a condensate with urea isabout 0.325 moles per mole of phenol in the phenol-formaldehyde resoleresin.

Once preparation of the phenol-formaldehyde resole resin as modifiedwith urea-aldehyde condensate (i.e., the modified phenolic-aldehyderesin) is complete, additional components may be added to adjust thedesired properties of the modified phenolic-aldehyde resin.Specifically, and in view of the high conversion of the components ofthe modified phenolic-aldehyde resin, a compatible plasticizing additivemay be combined with the modified phenolic-aldehyde resin to providedesirable melt-flow characteristics to the manufacturing compositionsprepared from the modified phenolic-aldehyde resin. Suitableplasticizers for use in the manufacturing compositions may be compatiblewith the modified phenolic-aldehyde resin, and may have low phaseseparation tendency and relatively high vapor pressure to mitigateemissions during subsequent processing. Suitable plasticizers may alsohave relatively low reactivity under the reaction conditions presentbetween the introduction of the plasticizer to form the manufacturingcompositions (the A staged resin) and the end-use high temperature andpressure cure of the manufacturing composition comprising the modifiedphenolic-aldehyde resin (the C staged resin). A desired property of theplasticizer is that it only condense with the manufacturing compositionmatrix under the end use conditions in forming an article, and retainflow and permeability properties during processing of the precure (alsoreferred to herein as the “B” stage) of the resin. Examples of suitableplasticizers include, but are not limited to, gum rosins, alcohols,ethylene glycol and oligomeric derivatives, propylene glycols andoligomeric derivatives, diethylene glycol, propylene glycol, 1,3-propanediol, glycerol, sorbitol, sugars, sugar alcohols, phenolic pot residuessuch as bisphenol A (BPA) and bisphenol F (BPF), low molecular weightphenolic compound-aldehyde novolaks, and soluble oligomers of phenoliccompounds, which may undergo only limited reaction prior to final cureat the C stage. A plasticizer may be added at about 0.1 to about 15 wt%, more specifically about 1 to about 5 wt %, of the total solidscharge.

A plasticizer, if added, may be dispersed in the matrix and allowed toreact in the presence of suitable concentrations of reactiveco-condensing monomer, such as an aldehyde, or it may be added andpermitted to disperse without co-condensing. Specifically, the aldehydemay comprise formaldehyde. Any condensation an aldehyde, such asformaldehyde, and a plasticizer may be limited by the concentration ofthe most reactive species. In one embodiment, a plasticizer is added toa modified phenolic-aldehyde resin composition medium. Dispersion of theplasticizer may be aided by heating the resulting composition from about25 to about 100° C., specifically about 50 to about 75° C., for about 1minute to about 1 hour, more specifically about 5 minutes to about 20minutes depending on the plasticizer.

A distillation step may be included, to adjust the solids content of themodified phenolic-aldehyde resin. Distillation is run for a timesufficient to collect about 10 to about 25% by weight, more specificallyabout 15 to about 18% by weight of the total mass charged, underconditions of about 45 to about 100° C., specifically about 50 to about85° C., and at about 633 to about 5 torr (about 5 to about 29.8 inchesHg of vacuum), more specifically about 379 to about 72.5 torr (about 15to about 27 inches Hg of vacuum).

Once preparation of the modified phenolic-aldehyde resin composition iscomplete, the mixture is cooled, for example to a temperature of about20 to about 50° C. Other additives may be included in the modifiedphenolic-aldehyde resin composition, such as a solution viscositymodifier or neutralizing acid. Suitable solution viscosity modifiers arelow molecular weight solvents miscible with the modifiedphenolic-aldehyde resin composition medium, and include lower alcohols.Examples of suitable lower alcohols include methanol, ethanol, propanol,butanol, pentanol, t-butanol, sec-butanol, isopropanol, isobutanol, andthe like. A specifically useful lower alcohol is methanol. The alcoholis added in an amount sufficient to achieve a viscosity in the modifiedphenolic-aldehyde resin composition of about 80 to about 20,000centipoise (cPs), specifically about 80 to about 400 cPs for typicalapplications. Acid may be added until a pH of about 5.5 to about 10 isachieved, to neutralize the modified phenolic-aldehyde resin compositionfor storage and handling and application requirements for cure. Thecooled mixture may be acidified using a strong acid such as sulfamicacid, sulfuric acid, formic acid, acetic acid, boric acid, phosphoricacid, lactic acid and the like, and mixtures thereof. Salts of theforegoing acids may also be used.

The mixture is further cooled, for example to a temperature of about 15to about 30° C. The modified phenolic-aldehyde resin composition, whichmay be an aqueous composition, can be used directly, or packaged, as bydrumming, and stored until needed or transferred to a site of intendeduse. Storage conditions are about 12 to about 22° C., and are similar tothe conditions for resins that are not so modified. Desirably, themodified phenolic-aldehyde resins are not infinitely dilutable in water(wherein “infinitely dilutable” means dilutable to a ratio of greaterthan about 50 parts water to about 1 part resin without evidence ofprecipitation of the resin), but maintain their solution stabilityduring shipping and storage at high solids (typically about 50 to about70% solids). Additionally, the higher solids compositions can bedelivered at lower freight costs to the customer. Other advantagesinclude less water is required to be removed by distillation since lesswater is added to the reaction mixture and the polymerization reactionproceeds more readily at higher solids.

The resulting modified phenolic-aldehyde resin composition can be usedto prepare a manufacturing composition or adhesive for a variety ofapplications. To make the completed manufacturing composition oradhesive composition, other additives, such as a catalyst, latent curecatalyst, or other additives such as filler, plasticizer, blowing agent,colorant, mold release agent, or the like, can be added to the modifiedphenolic-aldehyde resin composition. Latent catalysts neutralize thealkalinity of the modified phenolic-aldehyde resin upon heating andlower the pH to give an acid cure. Typical amounts are at least about 2wt %, specifically about 4 to about 10 wt %, based on the weight ofmanufacturing composition solids. Suitable latent catalysts includeammonium sulfate and the like. Such components may be added to themixture of modified phenolic-aldehyde resin composition shortly beforeuse. The manufacturing composition may then be contacted to a substratematerial. Such substrate materials may be cellulosic, where commoncellulosic materials include, but are not limited to paper, wood, woodflour, cotton, other vegetable fibers, coconut husk, ground nut shells,and the like. One application for the modified phenolic-aldehyde resinsdescribed above is in the manufacture of paper laminates. Typicaloverall molar ratios of formaldehyde to phenol in such modifiedphenolic-aldehyde resins may be about 0.9 to about 2.5 moles offormaldehyde per mole of phenol, specifically about 1.2 to about 1.9moles of formaldehyde per mole of phenol. Suitable catalyst levels areabout 0.2 to about 12 wt %, specifically about 0.5 to about 4 wt %.These materials may be used as synthesized, or an organic solvent suchas methanol can be added to reduce the percent solids and viscosity andaid in penetration of the kraft paper substrate.

Laminates may be made from several layers of paper that have beenimpregnated with thermosetting resins such as a modifiedphenolic-aldehyde resin as described hereinabove, dried (B-staged), andthen cured under pressure in a heated press. The surface of the laminateis made from a decorative paper (a solid color or printed with apattern) that is impregnated with a melamine-formaldehyde resin.Underneath this surface are several layers of kraft paper that areimpregnated with the above-described modified phenolic-aldehyde resin,and which function as a core for the laminate. The amount of modifiedphenolic-aldehyde resin solids incorporated into these papers variesfrom about 30 to about 80% based on the weight of the total laminate,and typically depends on the type of application and the type ofmaterials used to make the laminate.

Both the resin impregnated decorative paper and the resin impregnatedkraft core paper are passed through ovens to increase the molecularweight of the modified phenolic-aldehyde resin component, and reduce thevolatile level in the sheet (B-staging). After B-staging, a decorativesheet is laid up with several layers of the kraft core paper and loadedinto a press. The press is brought up to pressure, typically 1000 psi,when making high-pressure laminate and then heated up to temperaturestypically ranging from about 120 to about 160° C. for about 20 to about60 minutes. Such lamination consolidates the multiple paper layers andcures the modified phenolic-aldehyde resin components. At the end ofthat time period the press is cooled and the pressure is released.

A laminate made in this manner must then pass several physical tests,including impact resistance, abrasion resistance, blister resistance,ability to post-form, and resistance to boiling water. The presentcompositions comprising the modified phenolic-aldehyde resin providelaminates with low volatile emissions together with good physicalproperties.

In another embodiment, a laminate may be prepared for use in electricalgrade applications. The catalysts for these resins are understood to besubstantially free of metals for optimal dielectric properties, and mayinclude ammonia, hexamethylenetetramine, triethylamine, triethanolamine,and other types of amines. Minimization of free metal and metal ionsincrease the dielectric breakdown voltage, wherein a current is passedthrough the laminate at an increasing rate and specified time untilfailure or arcing through the dielectric or dielectric laminate occurs.

In another embodiment, the modified phenolic-aldehyde resin compositionsmay be used as adhesives in the manufacture of consolidated woodproducts such as plywood, engineered lumber, oriented strand board,particle board, and the like. In the manufacture of adhesives, themodified phenolic-aldehyde resin may be prepared having an overall molarratio of about 1.2 to about 3.5, specifically about 1.4 to about 2.5,more specifically about 1.8 to about 2.4 moles formaldehyde per molephenol, and an alkaline catalyst level of about 0.25 to about 1.0 molescatalyst per mole phenol. The pH of the modified phenolic-aldehyde resincomposition is typically from about 7.0 to about 12.0, specifically fromabout 10.0 to about 11.5. The modified phenolic-aldehyde resincomposition comprises about 40 to about 70 wt % solids, specificallyabout 55 to about 65 wt % solids. Adhesive mixtures typically containwater, extenders, fillers, caustic, performance additives, and modifiedphenolic-aldehyde resin. Typical fillers and extenders include corn,wheat, soya, and other cereal flours and derivatives, finely ground nutshells, barks, and agricultural furfural waste residues. The adhesivemixtures are then applied to plywood veneers and the veneers are thencombined in plies of three or more using a hot press to cure and bondthe adhesive. Methods of applying adhesive to plywood and pressing arewell known in the art.

An exemplary process for manufacture of a modified phenolic-aldehyderesin for laminates in accordance with this embodiment comprises forminga first aqueous reaction mixture by combining the phenol and the basiccatalyst (at about 0.05 moles per mole of phenol), applying about 125 toabout 72.5 torr (about 25 to about 27 inches Hg of vacuum) to thereactor, then feeding formaldehyde at an elevated temperature (e.g.,about 75 to about 80° C.) over about a 50-minute period. Theformaldehyde:phenol ratio may vary from about 1.05:1 to about 1.2:1. Theresin is maintained at this temperature for about 70 minutes.Condensation proceeds at about 78 to about 80° C. to a projectedendpoint having the desired free formaldehyde and phenol content. Atthis point in the process, free formaldehyde is about 0.10 wt % or less.An amount of urea-aldehyde condensate, specifically about 1 to about 16wt % depending on the application, is added over about a 15 minuteperiod, and the mixture is heated at about 78 to about 80° C. for about120 minutes. The free formaldehyde may be about 0.05 to about 0.12% atthis point in the process. Also at this point in the process, acompatible plasticizer may be added to the modified phenolic-aldehyderesin composition, and resulting mixture mixed at about 78 to about 80°C. for 10 minutes to disperse the plasticizer. The reaction issubsequently rapidly distilled, with the fraction collected distillinginitially at a head temperature of about 60° C., and is run for about 1to about 3 hours at a vacuum of about 15 to about 28 inches Hg ofvacuum, or for a time sufficient to collect about 10 to about 30%, morespecifically about 15 to about 25% of the total mass charged. Thereaction is heated at about 60° C. to about 77° C. to an endpoint wherethe water tolerance of the modified phenolic-aldehyde resin compositionis about 195% to about 205%. The heat is maintained for about 10 minutesbeyond this endpoint, and the reaction is cooled to about 65° C. atabout 125 torr (25 inches of Hg of vacuum). A viscosity-loweringcompatible solvent, such as methanol, is charged subsurface in an amountsufficient to achieve the desired final viscosity, and the reaction isrefluxed at about 50 to about 57° C. for about 10 minutes while mixing.The reaction is further cooled to about 40 to about 45° C., and aceticacid is added in an amount sufficient to adjust the pH of the modifiedphenolic-aldehyde resin composition from about 8 to about 9, andspecifically about 8.3 to about 8.7, and then cooled to shipping orstorage temperature (about 16 to about 22° C.). The refractive index ofthe modified phenolic-aldehyde resin composition may be between about1.52 and about 1.53 as measured at 25° C.

The water tolerance of the modified phenolic-aldehyde resin compositionfor purposes of determining the reaction end point is determined by thefollowing procedure a clean dry test tube with stir bar is place on atop pan balance and the Tare is balance to zero. Approximately 3-10 gramof resin sample is added to the test tube with disposable pipettes andthe record weight according to Table 1: TABLE 1 Expected Water ToleranceSample Weight 200% or less 10 g  300% 7 g 400% 6 g 500% 5 g 600% 4 g700% 3 gNext, 3-10 g of distilled or deionized water at 25.0° C.±0.1° C. isadded to the test tube with disposable pipette. For viscous samples thewater is added to the sample of modified phenolic-aldehyde resincomposition before the sample cools. The sample is thoroughly mixed withwater. For viscous samples, a test tube vortex mixer is used to agitatethe sample vigorously thoroughly and completely mixed with water. Ifsample does not mix, it is placed in a water bath at 60° C. for 30seconds, and vortex mixing is continued until mixing is complete. Thetest tube containing sample and any added water is then placed in awater bath at 25° C. on a stir plate for two minutes. Water is added tothe sample from a disposable pipette while agitating until the samplebegins to attain a cloudy appearance. The test end point (i.e., cloudpoint) occurs when small white alphanumeric characters on a blackbackground, initially visible through the sample, can no longer be readwhen viewed through the sample. When the end point is reached, the testtube containing the sample is removed from the water bath, the outsidesurface of the test tube is thoroughly dried, and the test tube andsample are re-weighed. The water tolerance is then calculated using thefollowing equation (note: the precision of the method is ±3%):$\quad{{{Water}\quad{Tolerance}\quad\left( {{in}\quad{wt}\quad\%} \right)} = \frac{{\begin{pmatrix}{{{final}\quad{sample}\quad{{wt}.\quad(g)}} -} \\{{initial}\quad{sample}\quad{{wt}.\quad(g)}}\end{pmatrix} \times 100}\quad}{\left( {{initial}\quad{sample}\quad{wt}\quad(g)} \right)}}$

In a particularly advantageous feature, the modified phenolic-aldehyderesin compositions may be used to manufacture products that maintaintheir desirable physical properties such as storage stability, moistureabsorption, ability to post-form, mar resistance, and the like. Inaddition, these desired properties may be maintained at low emissionslevels.

The urea-aldehyde condensate can also be used to prepare modifiedphenolic-aldehyde resins useful as saturating resins. Saturating resinsare used to saturate paper for oil filters, overlay paper, and paintroller tube applications. Saturating resins are typically lowformaldehyde-to-phenol ratio resole resins having about 0.8 to about 1.7moles formaldehyde per mole phenol. The low mole ratio resins give thetreated paper more flexibility for pleating before curing. Saturatingresins are usually higher molecular weight resins that have less than100% water tolerance. A distillation step is required and then thedistilled resin is dissolved in an alcohol such as methanol,isopropanol, or ethyl alcohol.

The resin is then applied to base paper, usually in dip roller pans, andthen the treated paper is heated in an oven to drive off solvent,resulting in “B” staged paper. The paper may then be rolled and providedto manufacturers to make articles for petroleum filtration (e.g., oilfilters). The paper is pleated, cut, and cured in an oven. The curedpaper has oil, temperature, water, and chemical resistant properties.Saturating resins for plywood overlays work in a similar way, except thetreated paper is not pleated but is bonded onto plywood or othersubstrate with heat and pressure, thereby curing the resin.

Some high f/p mole ratio saturating resins, typically having an f/pratio of 1.8:1 to 2.5:1 may be water soluble. Such resins, however, mustbe modified with a plasticizer such as a thermoplastic latex to give thetreated paper pleatability, as they are typically high in cross linkdensity and therefore are too brittle when cured in the absence ofplasticizer. The advantage in waterborne resins are no emissions fromsolvent and due to higher F/P mole ratios there will be less emissionsof free phenol.

Other uses for the urea-aldehyde condensate-modified phenol-formaldehyderesole resins (modified phenolic-aldehyde resins) include addition toabrasives coating resins as a modifier. Any phenol-formaldehyde resoleresin used as an abrasive or friction binder may be so modified.

Foams as used, for example, in the manufacture of foam blocks for thefloral industry, may also be produced using modified phenolic-aldehyderesin. Typically, phenol-formaldehyde resole resin foams range fromabout 1.7 to about 3.0 moles overall formaldehyde content per molephenol. The urea-aldehyde condensate can be used to modify aphenol-formaldehyde resole resin to provide the desired f/p ratio in themodified phenolic-aldehyde resin. Generally phenol and formaldehyde arereacted with a base catalyst to form the base resin. The resin is thenneutralized to a pH between about 6 and about 7 with an acid and wateris then distilled from the resin to a low water content, approximately 5to 15%. The resin typically has a high viscosity of about 2,000 to about20,000 cPs. Alternatively, urea may be added to scavenge formaldehyde inthese resins. A urea-aldehyde condensate may accordingly be added to thephenol-formaldehyde resole resin and urea premix. The importantreactivity characteristic of these resins is controlled by such factorsas the molecular weight, and the amounts of free monomer present.

In order to foam the resin, surfactants, and/or wetting agents are mixedinto the resin to create bubbles within the resin. A low boiling liquidsuch as CFC, HCFC, pentane, or hexane is added to the mixture. A strongacid is added to the resin to initiate curing of the phenol-formaldehyderesole resin. This reaction generates heat causing the low boilingliquid to vaporize within the bubbles in the resin. As a result a foamis created from this mixture. Within about 10 minutes the foam rises toits maximum height and hardens when fully cured.

It is also possible to use the modified phenol-formaldehyde resoleresins in the manufacture of acoustical ceiling tiles of the lay-intype. These are large rectangular interfelted cellulose or mineral fibermaterials with a starch binder, perforated on the face side forabsorption of sound. They are laid in hangers suspended from ceilingsand are only supported by their edges. An anti-sag coating of aheat-cured thermosetting resin may be applied on the back side toprevent sag, which tends to occur under conditions of high temperatureand humidity. The coating acts as a skin to hold the center of the tilein tension and provides the necessary support to keep the suspended tileflat. The modified phenol-formaldehyde resole resins may be combinedwith clay to form a coating that is applied to the ceiling tiles.Typical, but not limiting, resin-clay coating mixes are prepared with 4wt % clay and 1 wt % resin in a 55 wt % solids aqueous mixture. Themixes are then catalyzed with the appropriate amount of a suitablecatalyst such as ammonium sulfate to yield catalyzed resin-clayslurries.

Thus, in a particularly advantageous feature, the modifiedphenolic-aldehyde resins (modified with urea-aldehyde concentrate)disclosed herein have low free formaldehyde values throughout themanufacturing process and in the resulting compositions, up to andincluding manufacturing compositions, and shelf-life and physicalproperties that are lower than or at least comparable to unmodifiedphenol-formaldehyde resole resins and manufacturing compositionsprepared therefrom. The manufacturing compositions may also be used tomanufacture products that maintain their desirable physical propertiessuch as color, tensile strength, moisture resistance, compressionrecovery, post-form, pleatability and the like. The following examplesare for purposes of illustration and are not intended to limit the scopeof the claimed invention.

EXAMPLES Example 1 Preparation of Urea-Aldehyde Condensate

An example of the preparation of a urea-formaldehyde condensate is asfollows: A flask is charged with 124.5 g of a 50 wt % solution offormaldehyde, and the temperature of the solution is raised to about60-70° C. The formaldehyde solution is adjusted to a pH of about 8.5 toabout 9.2 by addition of about 0.7 g of 50 wt % sodium hydroxide inwater. About 25 g of urea is then added, and the temperature is slowlyraised to about 78° C. to about 82° C., and the temperature of thereaction is maintained at about 80° C. for a hold time of about 30minutes. During this hold, the pH is checked about every 10 minutes, andis adjusted to maintain a reaction pH of about 7.2 or greater byaddition of an effective amount of 25 wt % sodium hydroxide. After thehold time, the reaction is cooled to about 45° C. The reaction isdistilled under vacuum, and 52.4 g of distillate is collected to give arefractive index endpoint for the condensate of 1.469 to 1.472. Theamount of free formaldehyde is determined by sodium sulfite method to be22 wt % of the total mass of the condensate.

Example 2 Preparation of Phenol-Formaldehyde Resole Resin Modified withUrea-Aldehyde Condensate

A phenol-formaldehyde resole resin modified with a urea-aldehydecondensate is prepared as follows. First, 1427.1 g (15.164 moles) phenolis added to a reaction vessel, followed by addition of 57.1 g (0.714moles) of sodium hydroxide as a 50% aqueous solution, to provide 0.047moles of catalyst per mole of phenol, and mixing was begun. Antifoam(0.03 g) is added. The reaction temperature is adjusted to 75° C., andheat is removed when this temperature is reached. Aqueous 50%formaldehyde solution (1004.7 grams, 16.73 moles) is then added at acontrolled rate of about 20 g per minute over 50 minutes, until atemperature of 78-80° C. is obtained. At this point the quantity offormaldehyde charged to the reaction is 1.100 moles per mole of phenol.The mixture is allowed to react for a further 70 minutes whilemaintaining the temperature at 78-80° C. with vacuum reflux. At the endof this step in the process, the free (or unreacted) formaldehyde andphenol concentrations are 0.05% and 15.1%, respectively.

Next, 246.9 g of urea-formaldehyde condensate is added over a 15-minuteperiod while maintaining the temperature at 78-80° C. This mixture isallowed to react for 120 minutes. Based on literature and observation,it appears that little reaction occurs between the urea and phenolspecies under the conditions maintained during the current process.Therefore, the resin at this stage may be composed of primarily ofphenol-formaldehyde and, to a much lesser extent, urea-formaldehydespecies. The free formaldehyde and free phenol content of the product atthis stage are 0.15% and 10.25% by weight, respectively.

Next, the reaction is distilled to remove 526.6 g of distillate at atemperature of 55 to 66° C. using 86.7 torr (26.5 inches Hg of vacuum).The reaction is then heated to 77° C. and tested at about 15 minuteintervals until a water tolerance of 190% is obtained at a refractiveindex of 1.5862 at 25° C. (about 60 minutes hold time). During this holdat 77° C., it is believed that the various components in the mixturecontinue to undergo polymerization. In this test, water is added to asample of resin until a haze point is obtained. A specific ratio ofwater to resin is targeted as the endpoint. In this case, a haze pointat a ratio of two parts water to one part resin is targeted.

Vacuum reflux is used to cool the reaction to 65° C., and 498.1 gmethanol is added to give a viscosity of about 137 cPs. The reaction ismixed for 10 minutes at 50-57° C., then cooled to 40-45° C. Glacialacetic acid (21.4 g) is added to adjust the pH to 8.49, and the resin iscooled to 16-24° C. The methanol is added as a nonreactive diluent tolower the viscosity of the final resin product for ease of handling, toaid in the application of the resin to the paper substrate, and toreduce the amount of energy and time required to dry the impregnatedpaper. Acetic acid decreases the pH to give a pH dependent targetreactivity rate for the final product. The physical properties of thefinal resin are shown in Table 2 below: TABLE 2 Property Test ResultNonvolatiles (solids, %) 64.6 Viscosity (cPs) 137 pH 8.49 Free Phenol(%) 8.6 Free Formaldehyde (%) 0.05

Example 3 Preparation of Novolak Plasticizer

A reactor is charged with 1650.0 g phenol and 24.0 g of oxalic acid, andthe mixture is heated to 100° C. with stirring. A 50% aqueous solutionof formaldehyde (778.5 g) is fed into the reactor with stirring over 60minutes, at a feed rate of about 13 g per minute. After formaldehydeaddition is complete, the temperature is maintained for an additional 60minutes to increase the degree of condensation of the resin. Thereaction is distilled at atmospheric pressure to 160° C. to remove 673.5g of distillate. Distillation is continued under about 38 torr (28.5inches of vacuum) to a temperature of 190° C., and a second cut of 279.0g of distillate is collected, to give a free phenol level of less than0.7%. While hot, the resulting novolak resin is poured onto a pan tocool. The resin is allowed to cool, and is then broken up into flakeform. The flake resin is used as is in subsequent steps. The ratio offormaldehyde to free phenol in the final novolak resin is 0.74:1. Theproperties of the resin are provided in Table 3, below. TABLE 3 PropertyTest Result Nonvolatiles (solids, %) 99.7 Free Phenol (%) 0.3 FreeFormaldehyde (%) None detected

Example 4 Preparation of Phenol-Formaldehyde Resole Resin Modified withUrea-Aldehyde Condensate and Novolak Plasticizer

A phenol-formaldehyde resole resin modified with a urea-aldehydecondensate is prepared as follows. First, 47.0 g (0.499 moles) phenol isadded to a reaction vessel, followed by addition of 1.9 g (0.0238 moles)of 50% sodium hydroxide aqueous solution, to provide 0.0476 moles ofcatalyst per mole of phenol, and mixing was begun. The reactiontemperature is adjusted to 75° C., and heat is removed when thistemperature is reached. Aqueous 50% formaldehyde solution (33.0 grams,0.549 moles) is then added at a controlled rate of 0.7 g per minute over50 minutes, until a temperature of 80° C. is obtained. At this point thequantity of formaldehyde charged to the reaction is 1.10 moles per moleof phenol. The mixture is allowed to react for a further 70 minuteswhile maintaining the temperature at 80° C. with vacuum reflux.

Next, 8.1 g of the urea-aldehyde condensate is added over a 15-minuteperiod while maintaining the temperature at 80° C. This mixture isallowed to react for 120 minutes. The temperature is reduced to 60-65°C. and the reaction is distilled. A total of 17.3 g of distillate iscollected at 89 torr (26.5 inches of Hg of vacuum). The reaction is thenheated to 75-78° C. and reacted until a 190% water tolerance isobtained.

The reaction is cooled to 65° C., nitrogen is applied, and 19.6 gmethanol is added. The reaction is mixed for 10 minutes at 65° C., thencooled to 50-55° C. The novolak from Example 3 (7.0 g) is added to thereaction, and the reaction is agitated for 30 minutes to ensurehomogeneity. Glacial acetic (0.4 g) acid is added, and the modifiedphenolic-aldehyde resin composition is cooled to 16-24° C. The physicalproperties of the final resin are provided in Table 4, below. Theresulting modified phenolic-aldehyde resin composition may be used inthe preparation of resin impregnated papers for oil filters. TABLE 4Property Test Result Nonvolatiles (solids, %) 64.0 Viscosity (cPs) 240Refractive Index 1.5270 Free Phenol (%) 8.0 Free Formaldehyde (%) 0.05

Example 5 Preparation of Phenol-Formaldehyde Resole Resin Modified withUrea-Aldehyde Condensate and BPA Plasticizer

A phenol-formaldehyde resole resin modified with a urea-aldehydecondensate is prepared as follows. First, 51.1 g (0.544 moles) phenol isadded to a reaction vessel, followed by addition of 2.0 g (0.025 moles)of 50% sodium hydroxide aqueous solution, to provide 0.046 moles ofcatalyst per mole of phenol, and mixing was begun. Antifoam (0.001 g) isadded. The reaction temperature is adjusted to 75° C., and heat isremoved when this temperature is reached. Aqueous 50% formaldehydesolution (36.0 grams, 0.60 moles) is then added at a controlled rate of0.7 g per minute over 50 minutes, until a temperature of 78-80° C. isobtained. At this point the quantity of formaldehyde charged to thereaction is 1.103 moles per mole of phenol. The mixture is allowed toreact for a further 70 minutes while maintaining the temperature at78-80° C. with vacuum reflux. At the end of this step in the process,the free (or unreacted) formaldehyde and phenol concentrations are 0.0%and 19.3%, respectively.

Next, 8.8 g of the urea-aldehyde condensate (0.176 moles formaldehyde;0.037 moles urea) is added over a 15-minute period while maintaining thetemperature at 78-80° C. This mixture is allowed to react for 120minutes. The free formaldehyde and free phenol content of the product atthis stage are 0.1 and 12.2% by weight, respectively. Next, 2.6 gbisphenol A (BPA) is added as a plasticizer and mixed for 10 minutes,and the reaction is distilled to remove 18.9 g of distillate at atemperature of 60-65° C. using 112 to 86.7 torr (25.5 to 26.5 inches Hgof vacuum). The reaction is then heated to 75° C. and reacted until awater tolerance of about 195 to about 200% is obtained. The final molarratio of formaldehyde:urea:phenol is 1.33:0.07:1.00.

Vacuum reflux is used to cool the reaction to 65° C., and 17.8 gmethanol is added to give a viscosity of about 120 to about 170 cPs at arefractive index of about 1.520 to about 1.531. The reaction is mixedfor 10 minutes at 50-57° C., then cooled to 40-45° C. Glacial acetic(0.5 g) acid is added to adjust the pH to 8.3-8.7, and the resin iscooled to 16-24° C. The physical properties of the final resin areprovided in Table 5, below. TABLE 5 Property Test Result Nonvolatiles(solids, %) 65.2 Viscosity (cPs) 142 pH 8.5 Free Phenol (%) 9.2 FreeFormaldehyde (%) 0.05

Example 6 Preparation of Phenol-Formaldehyde Resole Resin Modified withUrea-Aldehyde Condensate and Gum Rosin Plasticizer

A phenol-formaldehyde resole resin modified with a urea-aldehydecondensate is prepared as follows. First, 50.6 g (0.538 moles) phenol isadded to a reaction vessel, followed by addition of 2.0 g (0.025 moles)of 50% sodium hydroxide aqueous solution, to provide 0.0465 moles ofcatalyst per mole of phenol, and mixing was begun. The reactiontemperature is adjusted to 75° C., and heat is removed when thistemperature is reached. Aqueous 50% formaldehyde solution (35.6 grams,0.593 moles) is then added at a controlled rate of about 0.7 g perminute over 50 minutes, until a temperature of 80° C. is obtained. Atthis point the quantity of formaldehyde charged to the reaction is 1.10moles per mole of phenol. The mixture is allowed to react for a further70 minutes while maintaining the temperature at 80° C. with vacuumreflux.

Next, 8.8 g of the urea-aldehyde condensate is added over a 15-minuteperiod while maintaining the temperature at 78-80° C. This mixture isallowed to react for 120 minutes. The temperature is reduced to 55-60°C. and the reaction is distilled. A total of 18.7 g of distillate iscollected at a vacuum of 99.5 torr (26.0 inches Hg of vacuum). Thereaction is then heated to 75° C. and reacted until a 190-200% watertolerance is obtained.

The reaction is cooled to 65° C., nitrogen is applied, and 17.7 gmethanol is added. The reaction is mixed for 10 minutes at 65° C., thencooled to 50-55° C. Gum rosin (3.2 g) is added to the reaction, and thereaction is agitated for 30 minutes to ensure homogeneity. The reactionis cooled to 40-45° C., and glacial acetic (0.5 g) acid is added, andthe modified phenolic-aldehyde resin composition is cooled to 25° C. Thefinal ratio of formaldehyde to phenol in the modified phenolic-aldehyderesin composition is 1.43:1. Physical properties of the final resin areprovided in Table 6, below. TABLE 6 Property Test Result Nonvolatiles(solids, %) 67.0 Viscosity (cPs) 200 pH 8.0 Free Phenol (%) 8.2 FreeFormaldehyde (%) 0.05

Example 7 Preparation of Phenol-Formaldehyde Resole Resin Modified withUrea-Aldehyde Condensate and Diethylene Glycol Plasticizer

A phenol-formaldehyde resole resin modified with a urea-aldehydecondensate is prepared as follows. First, 51.0 g (0.542 moles) phenol isadded to a reaction vessel, followed by addition of 2.0 g (0.025 moles)of 50% sodium hydroxide aqueous solution, to provide 0.0460 moles ofcatalyst per mole of phenol, and mixing was begun. The reactiontemperature is adjusted to 75° C., and heat is removed when thistemperature is reached. Aqueous 50% formaldehyde solution (35.9 grams,0.598 moles) is then added at a controlled rate of about 0.7 g perminute over 50 minutes, until a temperature of 80° C. is obtained. Atthis point the quantity of formaldehyde charged to the reaction is 1.10moles per mole of phenol. The mixture is allowed to react for a further70 minutes while maintaining the temperature at 78-80° C. with vacuumreflux.

Next, 8.8 g of the urea-aldehyde condensate is added over a 15-minuteperiod while maintaining the temperature at 78-80° C. This mixture isallowed to react for 120 minutes. The temperature is reduced to 55-60°C. and the reaction is distilled. A total of 18.8 g of distillate iscollected at a vacuum of 86.7 torr (26.5 inches Hg of vacuum). Thereaction is then heated to 75° C. and reacted until a 190-200% watertolerance is obtained.

The reaction is cooled to 65° C., nitrogen is applied, and 17.8 gmethanol is added. The reaction is mixed for 10 minutes at 65° C., thencooled to 50-60° C. Diethylene glycol (2.5 g) is added to the reaction,and the reaction is agitated for 10 minutes to ensure homogeneity. Thereaction is cooled to 4045° C., and glacial acetic (0.8 g) acid isadded, and the modified phenolic-aldehyde resin composition is cooled to25° C. The final ratio of formaldehyde to phenol in the modifiedphenolic-aldehyde resin composition is 1.43:1. Physical properties ofthe final resin are provided in Table 7, below. TABLE 7 Property TestResult Nonvolatiles (solids, %) 65.0 Viscosity (cPs) 140 pH 8.5 FreePhenol (%) 8.5 Free Formaldehyde (%) 0.05

Example 8 Preparation of Phenol-Formaldehyde Resole Resin Modified withUrea-Aldehyde Condensate and Sorbitol Plasticizer

A phenol-formaldehyde resole resin modified with a urea-aldehydecondensate is prepared as follows. First, 50.7 g (0.539 moles) phenol isadded to a reaction vessel, followed by addition of 2.0 g (0.025 moles)of 50% sodium hydroxide aqueous solution, to provide 0.0464 moles ofcatalyst per mole of phenol, and mixing was begun. The reactiontemperature is adjusted to 75° C., and heat is removed when thistemperature is reached. Aqueous 50% formaldehyde solution (35.7 grams,0.594 moles) is then added at a controlled rate of about 0.7 g perminute over 50 minutes, until a temperature of 80° C. is obtained. Atthis point the quantity of formaldehyde charged to the reaction is 1.10moles per mole of phenol. The mixture is allowed to react for a further70 minutes while maintaining the temperature at 78-80° C. with vacuumreflux.

Next, 8.8 g of the urea-aldehyde condensate is added over a 15-minuteperiod while maintaining the temperature at 78-80° C. This mixture isallowed to react for 120 minutes. The temperature is reduced to 55-60°C. and the reaction is distilled. A total of 18.8 g of distillate iscollected at a vacuum of 86.7 torr (26.5 inches Hg of vacuum). Thereaction is then heated to 75° C. and reacted until a 190-200% watertolerance is obtained.

The reaction is cooled to 65° C., nitrogen is applied, and 17.7 gmethanol is added. The reaction is mixed for 10 minutes at 65° C., thencooled to 50-60° C. Sorbitol (3.1 g) is added to the reaction, and thereaction is agitated for 30 minutes to ensure homogeneity. The reactionis cooled to 40-45° C., and glacial acetic (0.8 g) acid is added, andthe modified phenolic-aldehyde resin composition is cooled to 25° C. Thefinal ratio of formaldehyde to phenol in the modified phenolic-aldehyderesin composition is 1.43:1. Physical properties of the final resin areprovided in Table 8, below. TABLE 8 Property Test Result Nonvolatiles(solids, %) 65.1 Viscosity (cPs) 172 pH 8.5 Free Phenol (%) 8.4 FreeFormaldehyde (%) 0.05

Example 9 Preparation of a Comparative Example

A phenol-formaldehyde resole resin without a urea-aldehyde condensate isprepared as follows. First, 1200.0 g (12.75 moles) phenol is added to areaction vessel, followed by addition of 48.0 g (0.6 moles) of sodiumhydroxide as a 50% aqueous solution, to provide 0.047 moles of catalystper mole of phenol, and mixing was begun. Antifoam (0.03 g) is added.The reaction temperature is adjusted to 75° C., and heat is removed whenthis temperature is reached. Aqueous 50% formaldehyde solution (1095.6grams, 18.24 moles) is then added at a controlled rate of about 20 g perminute over 50 minutes, until a temperature of 78-80° C. is obtained. Atthis point the quantity of formaldehyde charged to the reaction is 1.43moles per mole of phenol. The mixture is allowed to react for a further120 minutes while maintaining the temperature at 78-80° C. with vacuumreflux. At the end of this step in the process, the free (or unreacted)formaldehyde and phenol concentrations are 0.25% and 9.65%,respectively. The water tolerance is 200%.

Next, the reaction is distilled to remove 563 g of distillate at atemperature of 49 to 66° C. using 86.7 torr (26.5 inches Hg of vacuum).A water tolerance of 190% is obtained.

If needed, vacuum reflux is used to cool the reaction to 65° C., and 420g methanol is added to give a viscosity of about 105 cPs. The reactionis mixed for 10 minutes at 50-57° C., then cooled to 40-45° C. Glacialacetic acid (16.0 g) is added to adjust the pH to 8.38, and the resin iscooled to 16-24° C. The physical properties of the final resin are shownin Table 9 below. TABLE 9 Property Test Result Nonvolatiles (solids, %)64.3 Viscosity (cPs) 105 pH 8.38 Free Phenol (%) 8.72 Free Formaldehyde(%) 0.20

As compared to Example 2, Table 2, the free formaldehyde of Example 9 is0.15% lower for about the same free phenol and water tolerance endpointwhen using the same molar amount of sodium hydroxide based on phenol.

The singular forms “a”, “an”, and “the” include plural referents unlessthe context clearly dictates otherwise. The endpoints of all rangesreciting the same characteristic or referring to the quantity of thesame component are independently combinable and inclusive of the recitedendpoint. All cited patents, patent applications, and other referencesare incorporated herein by reference in their entirety.

While typical embodiments have been set forth for the purpose ofillustration, the foregoing descriptions should not be deemed to be alimitation on the scope herein. Accordingly, various modifications,adaptations, and alternatives may occur to one skilled in the artwithout departing from the spirit and scope herein.

1. A method for the manufacture of a modified phenolic-aldehyde resincomposition, comprising: reacting a base with a phenolic compound toproduce a phenolate medium; adding an aldehyde source to the phenolatemedium wherein the initial mole ratio of aldehyde to phenolic compoundis about 0.7:1 to about 1.4:1; heating the aldehyde source and phenolatemedium for a time and at a temperature sufficient to yield analdehyde-phenolate medium with a level of free aldehyde of less thanabout 0.5% of the total mass on a liquids basis; adding a urea-aldehydecondensate to the aldehyde-phenolate medium; and condensing theresulting urea-aldehyde-phenolate medium, wherein the modifiedphenolic-aldehyde resin is not infinitely dilutable in water.
 2. Themethod of claim 1 wherein heating the aldehyde source and phenoliccompound is without an added aldehyde scavenger.
 3. The method of claim1 where the base is a primary, secondary, or tertiary amine; ammonium,alkylammonium, or arylalkylammonium hydroxide; ammonium or alkylammoniumcarbonate; alkali metal hydroxide; alkali metal carbonate; alkalineearth metal hydroxide; alkaline earth metal carbonate; transition metalhydroxide; transition metal carbonate; or a combination comprising atleast one of the foregoing bases.
 4. The method of claim 1 where themolar ratio of base to phenolic compound is about 0.01:1 to about 0.6:1.5. The method of claim 1 wherein the phenolic compound comprises asubstituted monophenolic compound, an unsubstituted monophenoliccompound, a substituted dihydric phenol compound, an unsubstituteddihydric phenol compound, a substituted polycyclic monophenol, aunsubstituted polycyclic monophenols, a phenolic oligomer, or acombination comprising at least one of the foregoing compounds.
 6. Themethod of claim 1 where the aldehyde source is a formaldehyde,acetaldehyde, propionaldehyde, furfuraldehyde, glutaraldehyde,benzaldehyde, paraformaldehyde, formalin, or a combination comprising atleast one of the foregoing.
 7. The method of claim 1 wherein thealdehyde source is formaldehyde and the phenolic compound is phenol. 8.The method of claim 1 where the temperature of heating the aldehyde andphenolate medium is about 50 to about 100° C.
 9. The method of claim 1where the aldehyde of the urea-aldehyde condensate is formaldehyde,acetaldehyde, propionaldehyde, furfuraldehyde, glutaraldehyde,benzaldehyde, or a combination comprising at least one of the foregoingaldehydes.
 10. The method of claim 1 where the molar ratio of aldehydeto urea in the urea-aldehyde condensate is about 3:1 to about 6:1. 11.The method of claim 1 where the weight ratio of urea-aldehyde condensateto the aldehyde-phenolate medium is about 1:99 to about 50:50.
 12. Themodified phenolic-aldehyde resin composition of claim 1 where the finalmolar ratio of aldehyde to phenolic compound in the modifiedphenolic-aldehyde resin is about 0.7:1 to about 4.5:1.
 13. The method ofclaim 1 further comprising adding a plasticizer to the modifiedphenolic-aldehyde resin composition.
 14. The method of claim 13 where aplasticizer is wood rosin, diethyleneglycol, sorbitol, bisphenol A,bisphenol F, phenolic compound-aldehyde novolak resins, ethylene glycol,oligomeric ethylene glycol derivatives, propylene glycol, oligomericpropylene glycol derivatives, sugars, sugar alcohols, guanamines,rosins, derivatized phenols, phenolic novolac resin or a combinationcomprising at least one of the foregoing.
 15. The method of claim 13,where the plasticizer comprises about 0.1 to about 15.0 wt % of solidsof the modified phenolic-aldehyde resin composition.
 16. The method ofclaim 1 where the modified phenolic-aldehyde resin composition has aviscosity of about 80 to about 20,000 cPs.
 17. The method of claim 1where the modified phenolic-aldehyde resin composition has a pH of about5.5 to about 10.0.
 18. A modified phenolic-aldehyde resin comprising thereaction product of the combination of: a phenolic compound; about 0.01to about 1.0 moles of base catalyst per mole of phenolic compound; analdehyde, wherein the initial molar ratio of aldehyde:phenolic compoundis about 0.7:1 to about 1.4:1; and a urea-aldehyde condensate, thecombination being reacted at a temperature of about 70 to about 90° C.for a time effective to form a modified phenolic-aldehyde resin that isnot infinitely dilutable in water, and wherein the final molar ratio ofaldehyde:phenolic compound in the modified phenolic-aldehyde resin isabout 0.7:1 to about 4.5:1.
 19. An article comprising the modifiedphenolic-aldehyde resin of claim
 18. 20. A composition comprising andadditive, and a modified phenolic-aldehyde resin composition comprisingthe reaction product of the combination of: a phenolic compound; about0.01 to about 1.0 moles of base catalyst per mole of phenolic compound;an aldehyde, wherein the molar ratio of aldehyde:phenolic compound isabout 0.7:1 to about 1.4:1; and a urea-aldehyde condensate, thecombination being reacted at a temperature of about 70 to about 90° C.for a time effective to form a modified phenolic-aldehyde resin that isnot infinitely dilutable in water.